Sound operated control system



Feb. 16, 1943. M, A. KERR SOUND OPERATED CONTROL SYSTEM Filed May 51, 1939 trol the operation .of various other devices which Patented Feb. 1c, 1943 SOUND ornaarsn CONTROL SYSTEM Maxwell A. Kerr, Collingswood, N. 3., assignor to Radio Corp ation of tion of Delaware.

America, a corpora- Application May 31, 1939, Serial No. 276,684

. 3 Claims. (Cl. 171-352) This invention relates to control systems or apparatus such as are operated in response to sound, and has for its principal objectthe provision of an improved system and method of operation whereby the operation of various types of apparatus may be more effectively controlled in response to sound or to currents of audio fre- -quency.

While the invention is illustrated as app to a fog signal system for guiding ships, it is obvious that its essential featureshave many useful applications where a desired eiiect is to be produced in response to the blast of a horn or to sound from any other type of control source.

Thus it may be utilized, for example, to switch a load device from the input to the output circuit Y of a vacuum tube amplifier, to control the operation of a public address system so that sound may be picked up at a desired point, and to conitis desired to actuate in response to sound or to currents of audio frequency. 7 v

, Inits more specific aspects, the invention is illustrated as applied to a signal system which is set into operation in response to'the sound oia ships fog horn and-functions to produce successivetrains of sound impulses indicating the position of a lighthouse, a lightship, a buoy or the like. Such a signal system includes a microphone 'or'sound pickup device which may also function as a sound reproducer, in which case the control system automatically switches the microphone microphones are also arranged to be connected I from the input circuit of a controlamplifier to the output circuit of a vacuum tube amplifier, vi-

brator-operated converter, motor-generator, or

- any other suitable alternating current source and vice versa.

Other features of the invention are (1)' a vacuum' tube amplifier which has its plate impedance and therefore its anode voltage varied in respouse to sound from the control source, (2) a control device which is triggered to pass current in response to a predetermined level of the amplifier anode potential, and (3) a relay which is operated in response to the control device current and functions (a) to disconnect the sound pickup. device from the amplifier input circuit, (b) to complete the circuit of a sound reproducer, (c) to initiate operation of a clockwork-mechanism whichiunctions to recycle the control amplifier after a suitable interval, and (d) to initiate op- .eration of a tone generator in case the sound emanating at the lighthouse or other control statrol, calibration and protective features, hereinafter described in detail.

The invention will be better understood from the following description considered in connection with the accompanying drawing, and its scope is indicated by the appended claims.

The single figure of the drawing is a wiring diagram of a fog signal system embodying the invention. a

This system includes a pair of sound pickup devices or microphones ii] and ii supplied with a continuous polarizing field by suitable permanent magnets mounted within them, the microphones being connected through contacts l2--l3 and i l-I5 of a relay operated switch It with the opposite 'end terminals H and It of the primary of an amplifier input transformer IS, the mid-terminal 20 of this primary being grounded at the terminal 2!, together with thelow voltage side of the microphones l0 and ii. These through leads 22, and 23 and a relay operated switch 24 to a tone generator 25 in case the micro-: phones are utilized to produce the sound-emanating at the control station and may be of any suit-,

able type, such asthat shownhior example, in the Hahninann et al. U. S. Patent No. 1,667,418 or the Giannini et al. U. S. Patent No. 2,252,846.

anode 35 and the cathode 3t, and with adetector circuit which includes the cathode 3t and the diode plates 36. 'As later described, the func-- tion of the detector is to apply to the-amplifier input circuit a negative bias potential whereby the potentialoi the-anode 35 isflmade morepositive in response to sound received at the microphones It) and ll. 7

Responsive to this variation in the direct current potential'of the anodett are a pair of parallel-connected electron discharge devices 31 and 38, which are provided with control electrode's or control anodes 39 and it connected to the amplifieranode 35 through a resistor. ti and the up per right hand contacts itilt of a calibration tio Also included in the system are other con- 66 switch 52. frhe; input circuit of the control {in vices i 33 is, oi course, completed through the cathode-anode circuit of the amplifier 33 and the ground terminal 2! l Beginning at the terminal 2!, the cathodeanode or plate circuit oi the control devices 31 and 38 includes the electron discharge path of these devices, a clockwork-operated switch 45, the operating solenoid iii of the switch I6, and a and the control anodes 39 and 40 of the control devices 37 and 38.

positive power supply terminal which may be maintained at a potential of the order of 135 volts.' While the solenoid 46 is also connected through an adjustable resistor 48, the operating coil as protective switch G-5L a callbration resistor 52, and the cathode-anode chcuit of the amplifier 33 to the power supply source, it should be understood that the current of the coil 36 is sufiiciently large to operate the switch iiionly when. current is transmitted through. the cathode-anode circuit oi the devices 31 and 39, which are provided in duplicate merely for the ins; reliability operation of open position by the plate current 1' and is operated to its closed 11. case the amplifier is rendered inoperativeby failureof the tube or filament or plate battery, in which case the local sound signal is continuously operated in its normal cycle until the neussary repairs are made. To this end, the circuit of the operating coil 53 of the switch 2% is completed through the switch 50-5I to the ground terminals 2i--26 on one side, and through the six-volt terminal at to the power supply source on the other side. switch 24! connects the direct current input terminals of the generator 25 to the power source through the six-vo1t terminal 5d, and the alternating current output terminals of the generator to the devices iii and H through the leads 22 and 23.

Operation of the switch 56 to its upper closed position also completes the circuit of the operating coil 53 of the switch 24 through the parallelconnected or duplicate contacts 55-56 and 5'l58 and, in addition, completes through the contacts ESQ-(3Q the circuit of a clockwork winding coil 55.

Included in the circuit of the clockwork winding coil 6-! is a switch 62-63, which is so mechan= ical-ly related or coupled to the switch 45 that the switch is momentarily opened just before the switch et -4331s closed, thisresult being effected through. a mechanism including an operating member (it which is biased to the closed position of the switch t2-63 by the clockwork operating spring 65.

7 mary winding ill of a transformer 63, through which they are coupled to the diode circuit of the device 33. Included in this diode or detector circuit are the secondary winding 63 and the resistor 3! which is also included in the amplifier input circuit and is shunted by a capacitor ill.

The resistor 29-40 and a capacitor 1| are provided for timing the rate of change in the potential of the amplifier anode 35. The time constant of the resistor ZQ-Bil and a capacitor 1! is preferably. several times greater than the time interval of the lowest audio frequency signal to be amplified. This time constant is adjusted to the required value by change in the movable contact position of the resistor 30. Besistor 4i and capacitor 11 also perform a similar Closure of the The inductor 12 and capacitor 13 are connected in shunt. to the primary circuit of the amplifier input transformer IQ, for the purpose of attenuating frequencies above 1000 cycles without appreciably affecting the response at lower frequencies. This is desirable in order to exclude the efiect of sounds of frequencies outside the range of the usual ships fog signal. Further attenuation of these undesired frequencies is produced by thecapacitors 14, 15 and 16.

The function of the resistor 4| connected in the output circuit of the control devices 31 and 38 and the capacitor." is to attenuate sudden voltage surges ortransients in the plate circuits or the amplifier before they reach the anodes of the control devices 31 and 38. This permits resetting of the amplifier by a momentary opening of the switch 45, for the reason that the voltage applied to the control electrodes of the devices 31 and 33' will not rise to the voltage of the amplifier anode 35 until the control devices 31 and 38 have had sufiicienttime to completely de-ionize before they are subjected to the normal standby voltage.

The calibration switch 42 is illustrated as in its normal position In its lower or calibrating position the secondary winding of the transformer I9 is short-circuited through the contacts 18-49,

/ andthe input of the control devices 31-and 38 is interrupted at the contacts 43-44 and is completed through the contacts 44-80 tothe. right hand end terminal of the resistor 52.

With these connections, the amplifier plate voltage of the device 33 is adjusted by (1) shift ing the movable contact, to include less, of the resistor 48 in the plate circuit until plate current starts through the device 31 or '38 and operates the sound reproducer, and (2) moving the switch 42 to its illustrated position. This adjustment leaves the amplifier output voltage at a. value,

about 6 volts lower than that required to initiate operation of the control devices 31 and 38, and permits "the system to be readily calibrated to compensate for decrease in the voltage 01 the power supply source, so that the system is always operated in response to the same range or signal intensities. 4

In the stand-by condition of the system, (1)

the operating coil 46 is not sufficiently energized to operate the switch l6 to its upper position, (2) v the clockwork-winding solenoid 6| is not energized, (3) the switches 45 and 62--63 are closed, l) the protective switch 50-5! is open, (5) the calibration switch 42 is in its illustrated position, (6) the operating coil 53 of-the switch 24 is not energized, and (7) no direct current is supplied to the generator 25.

When sound of the required frequency is picked up by thedevices lll'and II for a period of time dependent'lon the adjustment of the re- 3 sister 30, (1) the potential of the anode 35 is raised, (2) higher potential is applied to the con- I trol electrode 39 and 46 of the .control devices 31 and 38, (3) current starts through the cathode- I anode circuit of one of these control devices. and

(4) the switch lBis operated to its upper closed position.

I In this position of the switch, l6, (1-) the primary circuit of the amplifier input circuit is interrupted at the contacts l2-i3 and |4'l5, (2)

the circuit of the operating coil 53 of the" switch 24 is completed through the duplicate contacts function between the anode it of the amplifier 7:; Sli and 41-48. and (3) the circuit of the clockwork winding solenoid 55 is completed through the contacts sa es.

Operation of the switch 26 to its closed position connects the generator directcurrent input terminals to the 6-volt terminal of the power source and connects the alternating current output terminals to the microphones which then become reproducers or transmitters. With these connections, there is originated at the devices it and it sound of a tone dependent on the frequency of the generator 25.

It is desirable, however, that the local signal should continue in its normal train for a sufficient time to allow the passage of a ship andshould then terminate. This result is accomplished by a clockwork mechanism which includes a pawl and ratchet device 9!, 92 mechanically coupled to the control member 64 of the switches 45 and 82-83 in such a way that (1) switches 45 and 62-43 are closed during the stand-by period, (2) the clockwork spring 65 is wound sufficiently for one operating cycle in response to closure of the switch l8, (3) the switch 62-63 is opened in response to energization of the clockwork winding solenoid 6i, and (4) switch as is momentarily opened, as by means of a cam device 93, to recycle the amplifier just before switch e2ii3 is again closed. A suitable type of clockwork mech anism for this purpose is Ford Motor Company Part No. 81A-l5005-C when modified by the addition of switch 45, or it may be of the type shown and described either in the Eaton U. S. Patent No. 455,873 or the Banks U. S. Patent No. 587,693.

A more detailed description of the operation of the device is as follows: When sound of the required frequency is picked up by the devices l and H a corresponding A.-C. potential is impressed on the primary winding of the transformer l9 through input terminals 85-862I, the switch contacts l2-|3 and i i-45, and the transformer primary terminals l'I-lB-ZU. The

' transformer 19 provides a proper impedance match and voltage step up between the microphones ID and H and the high impedance input circuit to the amplifier tube 33. The potentiometer 28 functions as a sensitivity control for the amplifier 33. The amplified alternating current potential in the plate circuit of the amplifier 33 is coupled to the primary winding 61 of the transformer 68 through the capacitor 68, the majority of the A.-C. energy following the path through the capacitor 58 since this path has much lower impedance than the path formed by the calibrat= ing resistor 52, the relay coil 49, the plate volt age adjusting resistor 48, the relay coil 68, and the 135-v0lt battery; The impedance of the resistor i and the ca- 'iacitor I1 is also high with re spect to the impedance of the capacitor 66 and the primary winding 61. The transformer 88 provides a voltage step up and impedance match between the plate circuit of the amplifying tube 33 and the principal diode load formed by the resistor 31 and the capacitors Hi and 15. The two diode plates 38 in the amplifier tube 33 are connected in parallel for added reliability. The

- principal function of the capacitor is to aid in reducing the sensitivity of the system to frequen cies above the normal frequency range of fog signals.

The A.-C. voltage from the secondary winding 89 of the transformer 68 is rectified through the diode portion of the tube 33 and produces a D.-C. potential across the resistor 3!, the end of the resistor 3| which 68 becoming negative is connected to the winding with respect to the cathode 3d of the amplifier 33. This negative potential is impressed on the control grid 32 of the amplifier 33 through the timing resistors 29 and 30 and the sensitivity control resistor 28. The capacitor 1! and the resistors 29 and (it perform two functions, namely, (1) they filter the pulsating D.-C. across the resistor 3i before it reaches the grid 32, and (2) they provide an adjustable time delay between the time the D.-C. potential appears across the resistor 3| and the time it is impressed on the grid 32. This time delay is important in preventing the detectors 3'! and 38 from being triggered by sudden impulses of sound, such as a clap of thunder, a call of a bird, a rifle shot, or other random noises. It is thus necessary for the sound picked up by the microphones l0 and H to be sustained for two or more seconds in order to overcome the time delay caused by the resistors 29 and 30 and the capacitor II. A ship's fog signal has this characteristic. The negative voltage impressed on the control grid 32 causes the plate impedance of the amplifier 33 to increase and thus decreases the plate current.

The D.-C. resistance of the solenoid winding 66, the resistor 48, the solenoid winding 49 and the resistor 52 produces a voltage drop between the terminal ll of the power supply and the anode 35 of the amplifier 33 when plate current is flowing. As described heretofore, the amplifier 33 is calibrated by adjusting the potential of the anode 35 to a value which is a few volts below the potential required on the control anodes 39 and 40 of the devices 31 and 38 in order to trig er them.

A sustained sound signal picked up by the microphones l0 and H causes a decrease in the plate current of the amplifier 33, as described above. When the D.-C. resistance in the external plate circuit has not changed, a decrease in plate current will cause a decrease in voltage drop from the terminal 41 to the anode 35, and.

thus an increase in the plate potential between the anode 35 and the terminal 2| will result. This increase in plate potential is passed through the contacts 43- and the resistor M to cause the A.-C. voltage across the capacitor 11 to rise by the same amount after sumcient time has elapsed to overcome the time delay in the resistor an and the capacitor H. When the D.-C. potential across the capacitor ll has previously been adjusted to within a few volts of the amount required to trigger the control devices 31-38, this additional rise in voltage initiates a discharge between control anodes 39 and 60 and the cathodes 8| and 82 of the control devices 31 and 38, respectively. In turn, this initiates the main discharge between the main anodes 89 and 90 of the devices 31 and 38, respectively, and the cathodes BI and 82. I

The control devices 37 and 38 are similar to the RCA type OA4-G tubes or to the Western Electric type 313-0 tubes, and the published data shows that with A.-C. potentials up to approximately volts between the main anode and the cathode, no discharge will occur until the voltage between the control anode is raised to a value between '10 and 90 volts. The published data also shows that once this discharge is initiated, it will continue. The tube assumes a constant voltage drop of approximately '70 volts between the main anode and the cathode and continues to pass current until the plate supply voltage is lowered to less than '70 volts. The discharge through the tube then stops and remainsistopped until the plate supply is increased and until another discharge is initiated by the control anode. The clockwork functions to stop the discharge through the control devices 31 and 38 by momentarily opening the contacts 45, as heretofore described.

I claim as my invention:

1. In a combined signal receiving and signal transmitting system, the combination of an electro-acoustical converter adapted to convert sound into alternating current and vice versa, means for producing a potential in response to altemating current, means normally coupling said converter to said potential producing means whereby said potential producing means is responsive to the alternating current output of said converter, an alternating current signal generator, a control device coupled to said potential producing means and responsive topotentials produced thereby, said control device havinga 'normally closed output circuit including a relay which is energized by the output of said control device when the potential applied to said device by said potential producing means has reached a predetermined value, means for maintaining said relay energized independently of the operating condition of said potential producing means, switching mechanism operable in response to said relay to disconnect said converter from said potential producing means and to connect said converter to said generator upon energization of said relay, and means rendered operative upon energization of said relay for restoring said relay after a predetermined time interval to effect operation of said switching mechanism to disconnect said converter from said generator and reconnect it to said potential producing means.

2. The invention set forth in claim 1 characterized in that said potential producing means comprises a vacuum tube amplifier, and'characterized further in that said control device includes an electron discharge tube of the type which continues to discharge after being initially triggered, the input circuit oi. said discharge tube being connected to the output circuit of said amelectron discharge tube of the type which continues to discharge after being initially triggered, the input circuit of said discharge tube being connected to the output circuit of said amplifier and the output circuit of said discharge tube being connected to said relay, the operation of said discharge tube after being triggered causing said relay to become and remain energized, characterized further by the addition of a normally closed switch in the output circuit of said discharge tube, and characterized still further in that said means for opening said last named output circuit comprises a clockwork mechanism coupled to said switch and arranged to open said switch at the expiration of said predetermined time interval.

MAXWELL A. KERR. 

